Co-planar, near field communication telemetry link for an analyte sensor

ABSTRACT

An inductive sensor system for remote powering and communication with an analyte sensor (e.g., a fully implantable analyte sensor). The system may include an analyte sensor and transceiver. The system may be ferrite-enhanced. The transceiver may implement a passive telemetry for communicating with the analyte sensor via an inductive magnetic link for both power and data transfer. The link may be a co-planar, near field communication telemetry link. The transceiver may include a reflection plate configured to focus flux lines linking the transceiver and the sensor uniformly beneath the transceiver. The transceiver may include an amplifier configured to amplify battery power and provide radio frequency (RF) power to a transceiver antenna.

CROSS-REFERENCE TO RELATED APPLICATION

The present application a divisional of U.S. patent application Ser. No.14/453,230, filed on Aug. 6, 2014, which claims the benefit of priorityto U.S. Provisional Application Ser. No. 61/864,174, filed on Aug. 9,2013, both of which are incorporated by reference in their entireties.

BACKGROUND Field of Invention

The present invention relates generally to measuring an analyte in amedium of a living animal using a system including a transceiver and asensor. Specifically, the present invention relates to a co-planar, nearfield communication telemetry link between the transceiver and thesensor capable of transcutaneous communication.

Discussion of the Background

A sensor may be implanted within a living animal (e.g., a human) used tomeasure an analyte (e.g., glucose or oxygen) in a medium (e.g.,interstitial fluid (ISF), blood, or intraperitoneal fluid) within theliving animal. The sensor may include a light source (e.g., alight-emitting diode (LED) or other light emitting element), indicatormolecules, and a photodetector (e.g., a photodiode, phototransistor,photoresistor or other photosensitive element). Examples of implantablesensors employing indicator molecules to measure an analyte aredescribed in U.S. Pat. Nos. 5,517,313 and 5,512,246, which areincorporated herein by reference in their entireties.

There is presently a need in the art for an improved inductive magneticlink for both powering and communicating with an analyte sensor.

SUMMARY

The present invention overcomes the disadvantages of prior systems byproviding, among other advantages, an improved inductive magnetic linkfor both powering and communicating with an analyte sensor.

One aspect of the invention may provide a sensor system for detecting anamount or concentration of an analyte in vivo within a living organism.The sensor system may include an analyte sensor and a transceiver. Theanalyte sensor may include a sensor antenna. The transceiver may beconfigured to interface with the analyte sensor, and the transceiver mayinclude a transceiver antenna configured to convey a power signal to theanalyte sensor and to receive data signals from the analyte sensor. Thetransceiver antenna and sensor antenna may be configured to provide aco-planar, near field communication telemetry link between thetransceiver and the sensor capable of transcutaneous communication. Insome embodiments, the transceiver antenna and sensor antenna may becapable of transcutaneous communication across a distance greater thanor equal to 0.5 inches.

Another aspect of the invention may provide a transceiver forinterfacing with an analyte sensor. The transceiver may include aninterface device and a reflection plate. The interface device may beconfigured to convey a power signal to the analyte sensor and to receivedata signals from the analyte sensor. In some embodiments, thereflection plate may be configured to focus flux lines linking theinterface device and the analyte sensor uniformly beneath thetransceiver.

Still another aspect of the invention may provide a transceiver forinterfacing with an analyte sensor. The transceiver may include anantenna, a battery, and an amplifier. The antenna may be configured toconvey a power signal to the analyte sensor and to receive data signalsfrom the analyte sensor. The battery may be configured to providebattery power. The amplifier may be configured to amplify the batterypower and provide radio frequency (RF) power to the antenna. Theprovided RF power may be sufficient to power the analyte sensor at arequired range.

Yet another aspect of the invention is a transceiver for interfacingwith an analyte sensor. The transceiver may include an antenna, anantenna fault detection circuit, and a microcontroller. The antenna maybe configured to convey a power signal to the analyte sensor and toreceive data signals from the analyte sensor. The antenna faultdetection circuit configured to output a voltage proportional to a fieldstrength of the antenna. The microcontroller configured to measure thevoltage output by the antenna fault detection circuit and determinewhether the antenna is emitting a strong enough signal.

Further variations encompassed within the systems and methods aredescribed in the detailed description of the invention below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate various, non-limiting embodiments ofthe present invention. In the drawings, like reference numbers indicateidentical or functionally similar elements.

FIG. 1 is a schematic view illustrating a sensor system embodyingaspects of the present invention.

FIG. 2 illustrates a perspective view of a sensor embodying aspects ofthe present invention.

FIG. 3 illustrates an exploded view of a sensor embodying aspects of thepresent invention.

FIGS. 4 and 5 illustrate perspective views of sensor components withinthe sensor body/shell/capsule of a sensor embodying aspects of thepresent invention.

FIG. 6 illustrates a side view of a sensor embodying aspects of thepresent invention.

FIG. 7 illustrates a cross-sectional end view of a sensor embodyingaspects of the present invention.

FIG. 8 is cross-sectional, perspective view of a transceiver embodyingaspects of the invention.

FIG. 9 is an exploded, perspective view of a transceiver embodyingaspects of the invention.

FIGS. 10A and 10B illustrate an inductive element/antenna and reflectionplate of a transceiver embodying aspects of the invention.

FIG. 11 illustrates a co-planar configuration of a transceiver antennaand implanted sensor in a sensor system embodying aspects of the presentinvention.

FIG. 12 illustrates magnetic field simulations characterizing flux lineslinking a transceiver antenna and a sensor in a sensor system embodyingaspects of the present invention.

FIG. 13 is a schematic view illustrating a transceiver embodying aspectsof the present invention.

FIG. 14 is a schematic view illustrating a transceiver embodying aspectsof the present invention.

FIG. 15 is a schematic view illustrating an antenna fault detectioncircuit embodying aspects of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a schematic view of a sensor system embodying aspects of thepresent invention. In one non-limiting embodiment, the system includes asensor 100 and an external transceiver 101. In the embodiment shown inFIG. 1, the sensor 100 may be capable of implantation in a living animal(e.g., a living human). The sensor 100 may be implanted, for example, ina living animal's arm, wrist, leg, abdomen, peritoneum, or other regionof the living animal suitable for sensor implantation. For example, inone non-limiting embodiment, the sensor 100 may be implanted beneath theskin (i.e., in the subcutaneous or peritoneal tissues). In someembodiments, the sensor 100 may be an optical sensor (e.g., afluorometer). In some embodiments, the sensor 100 may be a chemical orbiochemical sensor.

A transceiver 101 may be an electronic device that communicates with thesensor 100 to power the sensor 100 and/or receive measurementinformation (e.g., photodetector and/or temperature sensor readings)from the sensor 100. The measurement information may include one or morereadings from one or more photodetectors of the sensor and/or one ormore readings from one or more temperature sensors of the sensors. Insome embodiments, the transceiver 101 may calculate analyte (e.g.,glucose or oxygen) concentrations from the measurement informationreceived from the sensor 100.

In some embodiments, the sensor system may provide real-time readings,graphs, trends, and/or analyte alarms directly to a user. The system maybe capable of being used in a home setting, and, in embodiments wherethe analyte is glucose, the system may aid people with diabetes inpredicting and detecting episodes of hypoglycemia and hyperglycemia. Thesystem may additionally or alternatively be capable of being used inclinical settings to aid health care professionals in evaluating analytecontrol. In contrast to analyte monitoring systems currently availableon the market, the transceiver 101 implements a passive telemetry forcommunicating with the analyte sensor 100 via an inductive magnetic linkfor both power and data transfer. The sensor 100 may include aninductive element 114, which may be, for example, a ferrite basedmicro-antenna. In some embodiments, the inductive element may beconnected to micro-fluorimeter circuitry (e.g., an applicationspecification integrated circuit (ASIC)) and a related optical detectionsystem of the sensor 100. The sensor 100 may not include a battery, and,as a result, the sensor 100 may rely on the transceiver 101 to providenecessary power and a data link to convey analyte-related data back totransceiver 101.

In one non-limiting embodiment, the sensor system may continually recordinterstitial fluid glucose levels in people with diabetes mellitus forthe purpose of improving diabetes management. The transceiver 101 may bewearable and may communicate with the sensor 100, which may be apassive, fully implantable sensor. In a non-limiting embodiment, theanalyte sensor 100 may have the approximate size of a grain of rice. Thetransceiver 101 may provide energy to run the sensor 100, which may ormay not have an internal power source (e.g., a battery), via a magneticfield. In some embodiments, the magnetic transceiver-sensor link can beconsidered as “weakly coupled transformer” type. The magnetictransceiver-sensor link may provide energy and a link for date transferusing, for example, amplitude modulation (AM). Although in someembodiments, data transfer is carried out using AM, in alternativeembodiments, other types of modulation may be used. The magnetictransceiver-sensor link may have a low efficiency of power transfer and,therefore, may require relatively high power amplifier to energize thesensor 100 at longer distances. In some non-limiting embodiments, thesensor system may use a frequency of 13.56 MHz, which can achieve highpenetration through the skin and is a medically approved frequency band,for power transfer.

In some non-limiting embodiments, the transceiver 101 may be a handhelddevice or an on-body/wearable device. For example, in some embodimentswhere the transceiver 101 is an on-body/wearable device, the transceiver101 may be held in place by a band (e.g., an armband or wristband)and/or adhesive (e.g., as part of a biocompatible patch), and thetransceiver 101 may convey (e.g., periodically, such as every twominutes, and/or upon user initiation) measurement commands (i.e.,requests for measurement information) to the sensor 100. In someembodiments where the transceiver 101 is a handheld device (e.g., asmartphone, a tablet, a medical application-specific handheld device, orother handheld computing device), positioning (i.e., hovering orswiping/waving/passing) the transceiver 101 within range over the sensorimplant site (i.e., within proximity of the sensor 100) may cause thetransceiver 101 to automatically convey a measurement command to thesensor 100 and receive a reading from the sensor 100.

In some embodiments, the transceiver 101 may include an inductiveelement 103, such as, for example, a coil. The transceiver 101 maygenerate an electromagnetic wave or electrodynamic field (e.g., by usinga coil) to induce a current in an inductive element 114 of the sensor100, which powers the sensor 100. The transceiver 101 may also conveydata (e.g., commands) to the sensor 100. For example, in a non-limitingembodiment, the transceiver 101 may convey data by modulating theelectromagnetic wave used to power the sensor 100 (e.g., by modulatingthe current flowing through a coil 103 of the transceiver 101). Themodulation in the electromagnetic wave generated by the transceiver 101may be detected/extracted by the sensor 100. Moreover, the transceiver101 may receive data (e.g., measurement information) from the sensor100. For example, in a non-limiting embodiment, the transceiver 101 mayreceive data by detecting modulations in the electromagnetic wavegenerated by the sensor 100, e.g., by detecting modulations in thecurrent flowing through the coil 103 of the transceiver 101.

The inductive element 103 of the transceiver 101 and the inductiveelement 114 of the sensor 100 may be in any configuration that permitsadequate field strength to be achieved when the two inductive elementsare brought within adequate physical proximity.

In some embodiments, the sensor 100 includes a sensor housing 102 (i.e.,body, shell, capsule, or encasement), which may be rigid andbiocompatible. In exemplary embodiments, sensor housing 102 may beformed from a suitable, optically transmissive polymer material, suchas, for example, acrylic polymers (e.g., polymethylmethacrylate (PMMA)).

In some embodiments, sensor 100 may include an analyte indicator. Insome non-limiting embodiments, the analyte indicator may be a polymergraft 106 coated, diffused, adhered, or embedded on at least a portionof the exterior surface of the sensor housing 102. The polymer graft 106may cover the entire surface of sensor housing 102 or only one or moreportions of the surface of housing 102. As an alternative to coating thegraft 106 on the outer surface of sensor housing 102, the graft 106 maybe disposed on the outer surface of the sensor housing 102 in otherways, such as by deposition or adhesion. In some embodiments, thepolymer graft 106 may be a fluorescent glucose indicating polymer. Inone non-limiting embodiment, the polymer is biocompatible and stable,grafted onto the surface of sensor housing 102, designed to allow forthe direct measurement of glucose in interstitial fluid (ISF), blood, orintraperitoneal fluid after implantation of the sensor 100.

In some embodiments, the analyte indicator (e.g., polymer graft 106) ofthe sensor 100 may include indicator molecules 104. The indicatormolecules 104 may be distributed throughout the entire graft 106 or onlythroughout one or more portions of the graft 106. The indicatormolecules 104 may be, for example, fluorescent indicator molecules orabsorption indicator molecules. In some embodiments, the indicatormolecules 104 may reversibly bind an analyte (e.g., glucose or oxygen).When an indicator molecule 104 has bound an analyte, the indicatormolecule may become fluorescent, in which case the indicator molecule104 is capable of absorbing (or being excited by) excitation light 329and emitting light 331. In one non-limiting embodiment, the excitationlight 329 may have a wavelength of approximately 378 nm, and theemission light 331 may have a wavelength in the range of 400 to 500 nm.When no analyte is bound, the indicator molecule 104 may be only weaklyfluorescent.

In some embodiments, the sensor 100 may include a light source 108,which may be, for example, a light emitting diode (LED) or other lightsource that emits radiation, including radiation over a range ofwavelengths that interact with the indicator molecules 104. In otherwords, the light source 108 may emit the excitation light 329 that isabsorbed by the indicator molecules in the matrix layer/polymer 104. Asnoted above, in one non-limiting embodiment, the light source 108 mayemit excitation light 329 at a wavelength of approximately 378 nm.

In some embodiments, the sensor 100 may also include one or morephotodetectors (e.g., photodiodes, phototransistors, photoresistors orother photosensitive elements). For example, in the embodimentillustrated in FIG. 1, sensor 100 has a first photodetector 224 and asecond photodetector 226. However, this is not required, and, in somealternative embodiments, the sensor 100 may only include the firstphotodetector 224. In the case of a fluorescence-based sensor, the oneor more photodetectors may be sensitive to fluorescent light emitted bythe indicator molecules 104 such that a signal is generated by aphotodetector (e.g., photodetector 224) in response thereto that isindicative of the level of fluorescence of the indicator molecules and,thus, the amount of analyte of interest (e.g., glucose).

Some part of the excitation light 329 emitted by the light source 108may be reflected from the polymer graft 106 back into the sensor 100 asreflection light 331, and some part of the absorbed excitation light maybe emitted as emitted (fluoresced) light 331. In one non-limitingembodiment, the emitted light 331 may have a different wavelength thanthe wavelength of the excitation light 329. The reflected light 333 andemitted (fluoresced) light 331 may be absorbed by the one or morephotodetectors (e.g., first and second photodetectors 224 and 226)within the body of the sensor 100.

Each of the one or more photodetectors may be covered by a filter 112(see FIG. 3) that allows only a certain subset of wavelengths of lightto pass through. In some embodiments, the one or more filters 112 may bethin glass filters. In some embodiments, the one or more filters 112 maybe thin film (e.g., dichroic) filters deposited on the glass and maypass only a narrow band of wavelengths and otherwise reflect most of thereceived light. In some embodiments, the filters may be thin film(dichroic) filters deposited directly onto the photo detectors and maypass only a narrow band of wavelengths and otherwise reflect most of thelight received thereby. The filters 112 may be identical (e.g., bothfilters 112 may allow signals to pass) or different (e.g., one filter112 may be a reference filter and another filter 112 may be a signalfilter).

In one non-limiting embodiment, the second (reference) photodetector 226may be covered by a reference photodiode filter that passes light at thesame wavelength as is emitted from the light source 108 (e.g., 378 nm).The first (signal) photodetector 224 may detect the amount of fluorescedlight 331 that is emitted from the molecules 104 in the graft 106. Inone non-limiting embodiment, the peak emission of the indicatormolecules 104 may occur around 435 nm, and the first photodetector 224may be covered by a signal filter that passes light in the range ofabout 400 nm to 500 nm. In some embodiments, higher glucoselevels/concentrations correspond to a greater amount of fluorescence ofthe molecules 104 in the graft 106, and, therefore, a greater number ofphotons striking the first photodetector 224.

In some embodiments, sensor 100 may include a substrate 116. In someembodiments, the substrate 116 may be a circuit board (e.g., a printedcircuit board (PCB) or flexible PCB) on which circuit components (e.g.,analog and/or digital circuit components) may be mounted or otherwiseattached. However, in some alternative embodiments, the substrate 116may be a semiconductor substrate having circuitry fabricated therein.The circuitry may include analog and/or digital circuitry. Also, in somesemiconductor substrate embodiments, in addition to the circuitryfabricated in the semiconductor substrate, circuitry may be mounted orotherwise attached to the semiconductor substrate 116. In other words,in some semiconductor substrate embodiments, a portion or all of thecircuitry, which may include discrete circuit elements, an integratedcircuit (e.g., an application specific integrated circuit (ASIC)) and/orother electronic components, may be fabricated in the semiconductorsubstrate 116 with the remainder of the circuitry is secured to thesemiconductor substrate 116, which may provide communication pathsbetween the various secured components. In some embodiments, circuitryof the sensor 100 may incorporate some or all of the structure describedin U.S. patent application Ser. No. 13/650,016, which is incorporatedherein by reference in its entirety, with particular reference to FIG.11D.

In some embodiments, the one or more photodetectors (e.g.,photodetectors 224 and 226) may be mounted on the semiconductorsubstrate 116, but, in some preferred embodiments, the one or morephotodetectors may be fabricated in the semiconductor substrate 116. Insome embodiments, the light source 108 may be mounted on thesemiconductor substrate 116. For example, in a non-limiting embodiment,the light source 108 may be flip-chip mounted on the semiconductorsubstrate 116. However, in some embodiments, the light source 108 may befabricated in the semiconductor substrate 116.

FIGS. 2-7 illustrate a non-limiting embodiment of a sensor 100 embodyingaspects of the present invention that may be used in the sensor systemillustrated in FIG. 1. FIGS. 2 and 3 illustrate perspective and explodedviews, respectively, of the non-limiting embodiment of the sensor 100.

In some embodiments, as illustrated in FIG. 3, the sensor 100 mayinclude one or more capacitors 118. The one or more capacitors 118 maybe, for example, one or more tuning capacitors and/or one or moreregulation capacitors. Further, the one or more capacitors 118 may be inaddition to one or more capacitors fabricated in the semiconductorsubstrate 116.

In some embodiments, as illustrated in FIG. 3, the sensor 100 mayinclude a reflector 119 (i.e., mirror). Reflector 119 may be attached tothe semiconductor substrate 116 at an end thereof. In a non-limitingembodiment, reflector 119 may be attached to the semiconductor substrate116 so that a face portion 121 of reflector 119 is generallyperpendicular to a top side of the semiconductor substrate 116 (i.e.,the side of semiconductor substrate 116 on or in which the light source108 and one or more photodetectors 110 are mounted or fabricated) andfaces the light source 108. The face 121 of the reflector 119 mayreflect radiation emitted by light source 108. In other words, thereflector 119 may block radiation emitted by light source 108 fromentering the axial end of the sensor 100.

According to one aspect of the invention, an application for which thesensor 100 was developed (although by no means the only application forwhich it is suitable) is measuring various biological analytes in theliving body of an animal (including a human). For example, sensor 100may be used to measure glucose, oxygen, toxins, pharmaceuticals or otherdrugs, hormones, and other metabolic analytes in, for example, the humanbody.

The specific composition of the polymer graft 106 and the indicatormolecules 104 may vary depending on the particular analyte the sensor isto be used to detect and/or where the sensor is to be used to detect theanalyte (e.g., in the in subcutaneous tissues, blood, or peritoneum).Preferably, however, graft 106 should facilitate exposure of theindicator molecules to the analyte. Also, it is preferred that theoptical characteristics of the indicator molecules (e.g., the level offluorescence of fluorescent indicator molecules) be a function of theconcentration of the specific analyte to which the indicator moleculesare exposed.

FIGS. 4 and 5 illustrate perspective views of the sensor 100. In FIGS. 4and 5, the sensor housing 102, filters 112, and the reflector 119, whichmay be included in some embodiments of the sensor 100, are notillustrated. As shown in the illustrated embodiment, the inductiveelement 114 may comprise a coil 220. In one embodiment, coil 220 may bea copper coil but other conductive materials, such as, for example,screen printed gold, may alternatively be used. In some embodiments, thecoil 220 is formed around a ferrite core 222. Although core 222 isferrite in some embodiments, in other embodiments, other core materialsmay alternatively be used. In some embodiments, coil 220 is not formedaround a core. Although coil 220 is illustrated as a cylindrical coil inFIGS. 4 and 5, in other embodiments, coil 220 may be a different type ofcoil, such as, for example, a flat coil.

In some embodiments, coil 220 is formed on ferrite core 222 by printingthe coil 220 around the ferrite core 222 such that the major axis of thecoil 220 (magnetically) is parallel to the longitudinal axis of theferrite core 222. A non-limiting example of a coil printed on a ferritecore is described in U.S. Pat. No. 7,800,078, which is incorporatedherein by reference in its entirety. In an alternative embodiment, coil220 may be a wire-wound coil. However, embodiments in which coil 220 isa printed coil as opposed to a wire-wound coil are preferred becauseeach wire-wound coil is slightly different in characteristics due tomanufacturing tolerances, and it may be necessary to individually tuneeach sensor that uses a wire-wound coil to properly match the frequencyof operation with the associated antenna. Printed coils, by contrast,may be manufactured using automated techniques that provide a highdegree of reproducibility and homogeneity in physical characteristics,as well as reliability, which is important for implant applications, andincreases cost-effectiveness in manufacturing.

In some embodiments, a dielectric layer may be printed on top of thecoil 220. The dielectric layer may be, in a non-limiting embodiment, aglass based insulator that is screen printed and fired onto the coil220. In an exemplary embodiment, the one or more capacitors 118 and thesemiconductor substrate 116 may be mounted on vias through thedielectric.

In the illustrated embodiment, the one or more photodetectors 110include a first photodetector 224 and a second photodetector 226. Firstand second photodetectors 224 and 226 may be mounted on or fabricated inthe semiconductor substrate 116.

FIGS. 6 and 7 illustrate side and cross-sectional views, respectively,of the sensor 100 according to one embodiment. As illustrated in FIGS. 6and 7, the light source 108 may be positioned to emit light that travelswithin the sensor housing 102 and reaches the indicator molecules 104 ofthe polymer graft 106, and the photodetectors 110, which may be locatedbeneath filters 112, may be positioned to receive light from theindicator molecules 104 of the polymer graft 106.

FIGS. 8 and 9 are cross-sectional and exploded views, respectively, of anon-limiting embodiment of the transceiver 101, which may be included inthe analyte monitoring system illustrated in FIG. 1. As illustrated inFIG. 9, in some non-limiting embodiments, the transceiver 101 mayinclude a graphic overlay 204, front housing 206, button 208, printedcircuit board (PCB) assembly 210, battery 212, gaskets 214, antenna 103,frame 218, reflection plate 216, back housing 220, ID label 222, and/orvibration motor 928. In a non-limiting embodiment, the transceiverelectronics may be assembled using standard surface mount device (SMD)reflow and solder techniques. In one embodiment, the electronics andperipherals may be put into a snap together housing design in which thefront housing 206 and back housing 220 may be snapped together. However,this is not required, and in some alternative embodiments, the fronthousing 206 and back housing 220 in another manner (e.g., ultrasonicwelding). In some embodiments, the full assembly process may beperformed at a single external electronics manufacturer. However, thisis not required, and, in alternative embodiments, the transceiver 101may be performed at one or more electronics manufacturers, which may beinternal, external, or a combination thereof. In some embodiments, theassembled transceiver may be programmed and functionally tested. In someembodiments, assembled transceivers 101 may be packaged into their finalshipping containers and be ready for sale.

In some embodiments, as illustrated in FIGS. 8 and 9, the antenna 103may be contained within the housing 206 and 220 of the transceiver 101.In some embodiments, the antenna 103 in the transceiver 101 may be smalland/or flat so that the antenna 103 fits within the housing 206 and 220of a small, lightweight transceiver 101. In some embodiments, theantenna 103 may be robust and capable of resisting various impacts. Insome embodiments, the transceiver 101 may be suitable for placement, forexample, on an abdomen area, wrist or an upper-arm of a patient body. Insome non-limiting embodiments, the transceiver 101 may be suitable forattachment to a patient body by means of a biocompatible patch.

FIGS. 10A and 10B illustrate a non-limiting embodiment of an inductiveelement 103 and reflection plate 216 of the transceiver 101. In somenon-limiting embodiments, the inductive element 103 may be a ferriteantenna. The reflection plate 216 may be made of metal (e.g., aluminum)and may cover all or a portion of the antenna 103. In some embodiments,the reflection plate 216 may have a square, rectangular, triangular,circular, oval, or any other shape suitable for covering all or aportion of the antenna 103. In some embodiments, as illustrated in FIG.10B, the reflection plate 216 may be shaped to leave a minimum spaceavailable for wiring (i.e., connecting the antenna 103 to the PCBassembly 210).

In some embodiments, the reflection plate 216 may be a rigid piece ofmetal and may have different auxiliary features, such as, for example,holes for mounting the reflection plate 216 to the enclosure and/or PCBassembly 210. However, it is not necessary that the reflection plate 216have holes, and it is not necessary that the reflection plate 216 berigid. For example, in alternative embodiments, the reflection plate 216may be flexible (e.g., kitchen aluminum foil) and may be used with aflexible antenna (e.g., a flexible ferrite antenna). The flexiblereflection plate/flexible antenna embodiment may allow the transceiverto more closely conform to the contours of the body. In someembodiments, the antenna 103 may be glued or taped to the reflectionplate 216 (e.g., with adhesive or a thin piece of tape/foam).

In some embodiments, the reflection plate 216 may increase theefficiency of the inductive element/antenna 103. For example, in onenon-limiting embodiment, the reflection plate 216 may increase thereading range of the transceiver 101 by up to 30% or more. Also, thereflection plate 216 may provide mechanical support. For example, insome non-limiting embodiments, the reflection plate 216 may keep theantenna 103 secure and in place so the antenna 103 does not move insidehousing 206 and 220, protect the antenna 103 against mechanical shocks,and/or protect the antenna 103 against random detuning by circuitcomponents of the transceiver (e.g., PCB assembly 210). However, it isnot necessary that the reflection plate 216 provide mechanical support,and, in some embodiments where the reflection plate 216 is flexible, thereflection plate 216 may keep antenna in place (i.e., lock it). However,in other alternative embodiments, the reflection plate 216 need not keepantenna 103 in place and clamping (e.g., plastic clamping) mayalternatively or additionally be used to keep the antenna 103 in place.

In some embodiments, the antenna system may be a scalable system. Thatis, the antenna 103 and reflection plate 216 can be smaller or biggerand still retain desired properties and performance.

FIG. 11 illustrates a co-planar configuration of a transceiver antenna103 and an antenna of an implanted sensor 100 in a sensor systemembodying aspects of the present invention. The illustratedconfiguration is co-planar because main axis of the transceiver antenna103 is parallel to the main axis of the antenna of sensor 100. Theillustrated configuration is not coaxial because the transceiver antenna103 and the antenna of sensor 100 do not share a common axis. In theillustrated configuration, a loosely coupled transformer (e.g.,transceiver antenna 103 of transceiver 101) communicatestranscutaneously across a distance “d” with an implanted sensor 100. Theco-planar inductive link has to transfer power and data transcutaneouslyto the sensor 100, which may be inserted in the interstitial space. Someembodiments of the present invention may boost the efficiency by usingone or more of (a) the reflection plate 216, (b) high quality factor (Q)and high permeability ferrite antennas, (c) a high-efficiency, highpower radio frequency (RF) amplifier, and (d) careful antenna design andimpedance matching.

FIG. 12 illustrates magnetic field simulations characterizing flux lineslinking the transceiver antenna 103 and the sensor 100 in across-section of the system illustrated in FIG. 11 with an embodiment ofthe transceiver 101 having a reflection plate 216. In particular, FIG.12 shows the effect of the reflection plate 216 on the flux lines, whichare focused uniformly beneath the transceiver 101. Thus, in someembodiments, the reflection plate 216 may help produce a strongerinductive link between the transceiver antenna 103 and the sensor 100.Moreover, the flux lines created by the transceiver 101 having thereflection plate 216 may allow for flexibility in the alignment of thetransceiver antenna 103 and sensor 100 and/or enable a wearable, patientplaced telemetry system.

In some embodiments, the sensor 100 may be equipped with highlyminiaturized coil antenna 114 on ferrite substrate (e.g., ferrite core222), and the ferrite substrate may greatly increase both theoperational and communication range. The antenna 103 may also beequipped with a ferrite substrate. The ferrite substrates may be high Qand high permeability ferrite substrates. The Q or quality factor is adimensionless parameter that describes how under-damped an oscillator orresonator is, or equivalently, characterizes a resonator's bandwidthrelative to its center frequency. Higher Q indicates a lower rate ofenergy loss relative to the stored energy of the resonator; theoscillations die out more slowly. Permeability is the degree ofmagnetization of a material in response to a magnetic field. In someembodiments, the ferrite substrates may help to decrease the overallsize of the transceiver antenna 103 and sensor antenna 114 whilemaintaining or even enhancing their performance. For example, in onenon-limiting embodiment, the ferrite substrates may be NiZn basedferrite materials.

FIG. 13 is a schematic view of an external transceiver 101 according toa non-limiting embodiment. In some embodiments, the transceiver 101 mayhave a connector 902, such as, for example, a Micro-Universal Serial Bus(USB) connector. The connector 902 may enable a wired connection to anexternal device, such as a personal computer or smart phone. Thetransceiver 101 may exchange data to and from the external devicethrough the connector 902 and/or may receive power through the connector902. The transceiver 101 may include a connector integrated circuit (IC)904, such as, for example, a USB-IC, which may control transmission andreceipt of data through the connector 902. The transceiver 101 may alsoinclude a charger IC 906, which may receive power via the connector 902and charge a battery 908 (e.g., lithium-polymer battery).

In some embodiments, the transceiver 101 may have a wirelesscommunication IC 910, which enables wireless communication with anexternal device, such as, for example, a personal computer or smartphone. In one non-limiting embodiment, the communication IC 910 mayemploy a standard, such as, for example, a Bluetooth Low Energy (BLE)standard (e.g., BLE 4.0), to wirelessly transmit and receive data to andfrom an external device.

In some embodiments, the transceiver 101 may include voltage regulators912 and/or a voltage booster 914. The battery 908 may supply power (viavoltage booster 914) to radio-frequency identification (RFID) reader IC916, which uses the inductive element 103 to convey information (e.g.,commands) to the sensor 101 and receive information (e.g., measurementinformation) from the sensor 100. In the illustrated embodiment, theinductive element 103 is a flat antenna. However, as noted above, theinductive element 103 of the transceiver 101 may be in any configurationthat permits adequate field strength to be achieved when brought withinadequate physical proximity to the inductive element 114 of the sensor100. In some embodiments, the transceiver 101 may include a poweramplifier 918 to amplify the signal to be conveyed by the inductiveelement 103 to the sensor 100.

The transceiver 101 may include a peripheral interface controller (PIC)microcontroller 920 and memory 922 (e.g., Flash memory), which may benon-volatile and/or capable of being electronically erased and/orrewritten. The PIC microcontroller 920 may control the overall operationof the transceiver 101. For example, the PIC microcontroller 920 maycontrol the connector IC 904 or wireless communication IC 910 totransmit data and/or control the RFID reader IC 916 to convey data viathe inductive element 103. The PIC microcontroller 920 may also controlprocessing of data received via the inductive element 103, connector902, or wireless communication IC 910.

In some embodiments, the transceiver 101 may include a display 924(e.g., liquid crystal display), which PIC microcontroller 920 maycontrol to display data (e.g., glucose concentration values). In someembodiments, the transceiver 101 may include a speaker 926 (e.g., abeeper) and/or vibration motor 928, which may be activated, for example,in the event that an alarm condition (e.g., detection of a hypoglycemicor hyperglycemic condition) is met. The transceiver 101 may also includeone or more additional sensors 930, which may include an accelerometerand/or temperature sensor, that may be used in the processing performedby the PIC microcontroller 920.

In some embodiments, the circuitry of the transceiver 101 may beconfigured to provide a strong enough magnetic field to provideoperating power to the sensor 100 over up to a required range (e.g., 0.5inches, 0.75 inches, or 1 inch or more). In some embodiments, theamplifier 918 provides the RF power transmitted through transceiverantenna 103 to the sensor antenna 114 in order to provide power to runthe sensor 100 and for the sensor 100 to transmit data back to thetransceiver 101. In some non-limiting embodiments, as illustrated inFIG. 14, the amplifier 918 of transceiver 101 may be a Class Eamplifier, which is a class of switching mode power amplifiers. See,e.g., N. O. Sokal and A. D. Sokal, “Class E—A New Class ofHigh-Efficiency Tuned Single-Ended Switching Power Amplifiers”, IEEEJournal of Solid-State Circuits, vol. SC-10, pp. 168-176, June 1975.HVK. A Class E amplifier may be characterized by high efficiency andlinear modulation characteristics and suitable for the inductive loadapplications. In embodiments where the amplifier 918 is a Class Eamplifier, the amplifier 918 may provide maximum output power for agiven antenna 103 and battery 908 and/or an increase in reading range(e.g., a reading range of up to 1 inch or more). However, the amplifier918 is not required to be a Class E amplifier, and, in some alternativeembodiments, the amplifier 918 may be a different type of amplifier,such as, for example and without limitation, a Class D amplifier or aClass F amplifier.

In some embodiments, the transceiver 101 may include one or moreauxiliary sub-circuits. In some non-limiting embodiments, as illustratedin FIG. 14, the auxiliary sub-circuits may include one or more of anamplifier driver sub-circuit 932, shutdown safety circuit 934, a 7Cfilter (i.e., pi filter or capacitor-input filter) 936, antenna matchingcircuit 938, antenna fault detection circuit 940, and externaldemodulator circuit 942. The amplifier driver sub-circuit 932 may beconfigured to match an output impedance of the RFID reader IC 916 withthe input impedance of the amplifier 918. In one non-limitingembodiment, the amplifier driver sub-circuit 932 may be configured todrive a MOSFET's gate in the amplifier 918 in order to match bothMOSFET's gate input impedance and the RFID reader IC 916 outputimpedance and increase gate driving voltage. The amplifier driversub-circuit 932 may allow driving the gate with high voltage (e.g., 11Vpp), which may lead to decreased losses in MOSFET, maximum efficiencyof amplifier, and a longer sensor reading range. The shutdown safetycircuit 934 may be a hardware “fuse” to shut down the amplifier 918 toprevent excessive heating of the transceiver antenna 103 if thetransceiver software gets locked and the field stays on. By preventingexcessive heating of the transceiver antenna 103, the shutdown safetycircuit 934 prevents possible damage to the transceiver circuitry (e.g.,PCB assembly 210), data collection problems, and/or user discomfort thatmay be caused by excessive heating of the transceiver antenna 103. Insome embodiments, the shutdown safety circuit 934 may shut down theamplifier 918 after a predetermined amount of time (e.g., 400 ms). The πfilter 936 may filter higher harmonics. The antenna matching circuit 938may provide good matching between the output impedance of amplifier 918and the input impedance of antenna 103 and lead to maximized powerefficiency. The antenna fault detection circuit 940 may provide anindication of an antenna failure/no power mode. In some embodiments, theantenna fault detection circuit 940 may be a “sniffer” that uses aregular inductor (placed in vicinity of antenna) to detect the antennafield and detect its changes. The demodulator circuit 942 may demodulatedata received from the sensor 100.

The antenna fault detection circuit 940 may provide an indication whenthe antenna 103 is not emitting a strong enough RF signal (e.g., becausethe antenna 103 is broken or there are other hardware issues). In someembodiments, the antenna fault detection circuit 940 does not simplymeasure the output voltage of the amplifier 918 because the outputvoltage of the amplifier 918 does not provide sufficient information. Insome embodiments, even the power consumption of the amplifier 918 has nostraight dependence from the actual power emitted from the antenna 103.For instance, in some non-limiting embodiments, when the amplifieroutput is open, DC power consumption may be almost the same as withnormal working antenna (e.g., 2 W to 3 W, and, when the amplifier outputis shorted, consumption is very low (e.g., 0.2 W to 0.3 W). Accordingly,in some embodiments, instead of simply measuring the output voltage orpower of the amplifier 918, the antenna fault detection circuit 940 mayinclude an RF receiver (e.g., implemented on the PCB as part of the PCBcircuit assembly 210) having a voltage output proportional to the RFfield of the transceiver antenna 103.

FIG. 15 is a schematic view illustrating a non-limiting embodiment ofantenna fault detection circuit 940. As illustrated in FIG. 15, theantenna fault detection circuit 940 may include an unshielded inductorL107, which may have, for example, an 0805 size but may also be smalleror bigger). In some embodiments, the unshielded inductor L107 may be aferrite core inductor. The unshielded inductor L107 may act as smallreceiving antenna (i.e., a “sniffer”). The direction of the core ofinductor L107 may be the same as the direction of the magnetic field ofthe transceiver antenna 103. In some embodiments, the inductor L107 isnot placed at the center of the antenna surface where the receivedsignal is lowest. In preferred embodiments, the inductor L107 may beplaced close to the perimeter of the surface of antenna 103.

In some embodiments, the antenna fault detection circuit 940 may includea capacitor C75, a Schottky barrier diode D103, capacitor C76, andresistor R62. The inductor L107 and capacitor C75 with the internalcapacity of the Schottky barrier diode D103 may form a resonant circuitat frequency close to 13.56 MHz. However, this is not required, and, inalternative embodiments, the antenna fault detection circuit 940 mayinclude a resonant circuit at a different frequency. In somenon-limiting embodiments, for increased resonant frequency accuracy, theinductor L107 may have a 5% tolerance, and the capacitor C75 may have a2% tolerance. In other embodiments, different tolerances may be used.The capacitor C76 may filter the rectified RF signal, and the resistorR62 may act as a load in order to have the output voltage proportionalto the antenna field strength.

In some embodiments, the output from the antenna fault detection circuit940 may be fed to an analog input (e.g., analog to digital converter(ADC) input) of the microcontroller 920 for voltage measurement (seeFIGS. 13 and 14). Based on the voltage measurement, the microcontroller920 may determine whether the antenna 103 is emitting a strong enough RFsignal (e.g., by comparing the measured voltage to a minimum expectedvoltage). In one non-limiting embodiment, the output from the antennafault detection circuit 940 may be fed through a standardamplifier/buffer (not shown in FIG. 15) (e.g., with gain K=1) beforebeing fed to the analog input of the microcontroller 920 for voltagemeasurement. However, the standard amplifier/buffer is not necessary(the input resistance of the microcontroller 920 may be around 10 kOhm,and no significant signal attenuation may occur), and, in someembodiments, the antenna fault detection circuit 940 may not include thestandard amplifier/buffer. In some embodiments, the value of resistorR62 could be increased to compensate for an additional load from the ADCpin of the microcontroller 920. For other types of microcontrollers, thedesign of the antenna fault detection circuit 940 may be further tweakedto obtain optimum results (or amplifier/buffer could be used).

In some embodiments, as illustrated in FIG. 14, the amplifier 918 mayfeed directly from the battery 908 instead of relying on an intermediateboost converter (e.g., voltage booster 914) or other circuits. In theseembodiments, the transceiver 101 may not include a boost converter(e.g., voltage booster 914). By feeding directly from the battery 908,the amplifier 918 may increase the efficiency of the battery 908, whichwould increase the expected battery life, and may enable the transceiver101 to be smaller and cheaper as fewer components will be used. In someembodiments, the components of the configuration illustrated in FIG. 14may be small components decrease the overall size and power requirementsof the transceiver 101.

In some non-limiting embodiments, the amplifier 918 (e.g., a Class D, E,or F amplifier) and corresponding matching network illustrated in FIG.14 may provide sufficient power to the sensor 100 at a required range(e.g., ≥0.5 inch). In one non-limiting embodiment, the output of theamplifier 918 may be a voltage between 3.4V and 4.2V and a power between1.1 W and 1.5 W. However, in other non-limiting embodiments, theamplifier 918 may output a different voltage and/or power. In someembodiments, the amplifier 918 may be powered directly from the battery908 (as illustrated in FIG. 14) in order to increase efficiency andrecharge cycle length. In some non-limiting embodiments, back-scatteredAM modulation may be used to receive data from the sensor 100. Becauseits amplitude is very small, the transceiver demodulator circuit 942 maybe carefully designed and tuned in order to achieve a high (e.g., ≥95%)reading success ratio. In some non-limiting embodiments, the transceiver101 may be capable of operating with sensor distances from skin surfacethat exceed 0.5 inch, where the signal to noise ratio may dropsignificantly.

Embodiments of the present invention have been fully described abovewith reference to the drawing figures. Although the invention has beendescribed based upon these preferred embodiments, it would be apparentto those of skill in the art that certain modifications, variations, andalternative constructions could be made to the described embodimentswithin the spirit and scope of the invention.

What is claimed is:
 1. A transceiver for interfacing with an analytesensor, the transceiver comprising: an interface device configured toconvey a power signal to the analyte sensor and to receive data signalsfrom the analyte sensor; and a reflection plate configured to focus fluxlines linking the interface device and the analyte sensor uniformlybeneath the transceiver.
 2. The transceiver of claim 1, wherein thereflection plate is rigid.
 3. The transceiver of claim 1, wherein thereflection plate is flexible.
 4. The transceiver of claim 1, wherein thereflection plate is metal.
 5. The transceiver of claim 4, wherein thereflection plate is aluminum.
 6. The transceiver of claim 1, wherein theinterface device is an antenna.
 7. The transceiver of claim 6, whereinthe antenna has a ferrite core.
 8. The transceiver of claim 7, whereinthe ferrite core has a high quality factor and a high permeability. 9.The transceiver of claim 7, wherein the ferrite core is an NiZn basedferrite material.
 10. The transceiver of claim 6, wherein the antenna isa flat antenna.
 11. The transceiver of claim 1, wherein the reflectionplate increases the efficiency of the interface device.
 12. Thetransceiver of claim 1, wherein the reflection plate covers at least aportion of the interface device.
 13. The transceiver of claim 1, whereinthe interface device is attached to the reflection plate.
 14. Thetransceiver of claim 2, wherein the reflection plate provides mechanicalsupport for the interface device.
 15. The transceiver of claim 1,further comprising a printed circuit board (PCB) assembly, wherein thereflection plate protects the interface device from random detuningcaused by the PCB assembly.
 16. A transceiver for interfacing with ananalyte sensor, the transceiver comprising: an antenna configured toconvey a power signal to the analyte sensor and to receive data signalsfrom the analyte sensor; a battery configured to provide battery power;an amplifier configured to amplify the battery power and provide radiofrequency (RF) power to the antenna, wherein the provided RF power issufficient to power the analyte sensor at a required range.
 17. Thetransceiver of claim 16, wherein the amplifier is a Class E amplifier.18. The transceiver of claim 16, wherein the required range is greaterthan or equal to 0.5 inches.
 19. The transceiver of claim 16, whereinthe required range is greater than or equal to one inch.
 20. Thetransceiver of claim 16, wherein the battery is a lithium-polymerbattery.
 21. The transceiver of claim 16, wherein the antenna has aferrite core.
 22. The transceiver of claim 21, wherein the ferrite corehas a high quality factor and a high permeability.
 23. The transceiverof claim 21, wherein the ferrite core is an NiZn based ferrite material.24. The transceiver of claim 16, wherein the antenna is a flat antenna.25. The transceiver of claim 16, further comprising a housing, whereinthe antenna is contained within the housing.
 26. The transceiver ofclaim 16, further comprising an antenna fault detection circuitconfigured to provide an indication that the antenna failed to conveythe power signal to the analyte sensor.
 27. The transceiver of claim 16,further comprising a shutdown safety circuit configured to shut down theamplifier if the amplifier provides the RF power to the antenna for apredetermined amount of time.
 28. The transceiver of claim 16, furthercomprising a pi filter configured to high harmonics.
 29. The transceiverof claim 16, further comprising an antenna matching circuit configuredto provide good matching between an output impedance of the amplifierand an input impedance of the antenna.
 30. The transceiver of claim 16,further comprising an radio-frequency identification (RFID) integratedcircuit (IC) configured to encode data to be conveyed to the analytesensor and to decode data received from the analyte sensor.
 31. Thetransceiver of claim 30, further comprising an amplifier drivesub-circuit configured to match an input impedance of the amplifier andan output impedance of the RFID IC.
 32. The transceiver of claim 16,wherein the amplifier feeds directly from the battery and does rely onan intermediate boost converter.
 33. A transceiver for interfacing withan analyte sensor, the transceiver comprising: an antenna configured toconvey a power signal to the analyte sensor and to receive data signalsfrom the analyte sensor; an antenna fault detection circuit configuredto output a voltage proportional to a field strength of the antenna; anda microcontroller configured to measure the voltage output by theantenna fault detection circuit and determine whether the antenna isemitting a strong enough signal.
 34. The transceiver of claim 33,wherein antenna fault detection circuit comprises an unshielded inductorconfigured to act as a receiving antenna.
 35. The transceiver of claim34, wherein the unshielded inductor has a ferrite core.
 36. Thetransceiver of claim 34, wherein antenna fault detection circuit furthercomprises a capacitor and a diode, wherein the inductor, capacitor, anddiode form a resonant circuit.